This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A386550 #19 Aug 03 2025 17:49:07 %S A386550 0,2,176,17222,1687556,165363242,16203910136,1587817830062, %T A386550 155589943435916,15246226638889682,1493974620667752896, %U A386550 146394266598800894102,14345144152061819869076,1405677732635459546275322,137742072654122973715112456,13497317442371415964534745342 %N A386550 Indices of hexagonal numbers that are six times another hexagonal number. %H A386550 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (99,-99,1). %F A386550 a(n) = (3*A269551(n-2) - 7)/4 for n>=2. - _Hugo Pfoertner_, Jul 26 2025 %F A386550 G.f.: 2*x^2*(1 - 11*x - 2*x^2)/((1 - x)*(1 - 98*x + x^2)). - _Stefano Spezia_, Jul 27 2025 %e A386550 176 is in this sequence because the 176th hexagonal number (61776) is six times another hexagonal number. %Y A386550 Cf. A000384, A269551, A385917, A386549. %K A386550 nonn,easy %O A386550 1,2 %A A386550 _Kelvin Voskuijl_, Jul 25 2025 %E A386550 More terms from _Jinyuan Wang_, Jul 26 2025